The present invention relates generally to the coupling of ceramic members to metal members. More specifically, the invention relates to a turbomachine including a ceramic nozzle that is coupled to a metal turbine housing.
Turbopumps are typically used for pumping fuel and oxidant to rocket engines. Rocket engine turbopumps are designed to operate at high shaft speeds and high horsepower in order to deliver high flow rates to the rocket engines.
A typical rocket engine turbopump includes a combustor and at least one turbine stage. In the first turbine stage, a nozzle directs hot, expanding gas from the combustor onto a rotor. The directed gas causes the rotor to rotate and create shaft work. The shaft work is used to pump the fuel and oxidant to the rocket engine.
The nozzle, which is secured to a turbine housing, is stationary with respect to the rotor. The nozzle directs the gas onto rotor vanes at an angle that produces maximum torque.
However, directing the gases creates a torque reaction on the nozzle. Torque on the nozzle can become extremely high, approaching several thousand foot-pounds. Such high torque is reacted by the turbine housing. Consequently, securing the nozzle to the turbine housing and keeping the nozzle stationary becomes a problem. Conventional approaches such as clamping the nozzle to the turbine housing and relying on friction to keep the nozzle stationary are ineffective.
Keeping the nozzle stationary becomes even more difficult if the nozzle and turbine housing are made of materials having different coefficients of thermal expansion. If the housing is made of metal and the nozzle is made of ceramic, the nozzle will expand at a different rate than the housing.